The present application relates to a negative electrode, a nonaqueous electrolyte secondary battery and a method for manufacturing a nonaqueous electrolyte secondary battery.
In more detail, the present application relates to a negative electrode including a negative electrode collector and a negative electrode active material layer covering at least one principal plane of the negative electrode collector and containing at least a negative electrode active material, in which the negative electrode active material contained in a region of up to at least 50% of a thickness from the surface of the negative electrode active material layer is covered with a solid electrolyte interface coating, and the solid electrolyte interface coating contains a product with a crosslinked isocyanate group in an isocyanate compound; a nonaqueous electrolyte secondary battery; and a method for manufacturing a nonaqueous electrolyte secondary battery.
In recent years, a number of portable electronic appliances such as a camera-integrated video tape recorder, a digital still camera, a mobile phone, a personal digital assistant and a laptop computer have appeared, and it is contrived to achieve downsizing and weight reduction thereof.
With respect to batteries, in particular, secondary batteries as a portable power source for such a portable electronic appliance, research and development have been actively conducted for the purpose of enhancing the energy density.
Above all, lithium ion secondary batteries using a carbon material for a negative electrode active material, a complex material of lithium (Li) and a transition metal for a positive electrode active material and a carbonate mixture for an electrolytic solution are widely put into practical use because a large energy density is obtained as compared with lead batteries and nickel-cadmium batteries which are an aqueous electrolytic solution secondary battery of the related art.
In particular, laminate type batteries using an aluminum laminated film for an exterior member are lightweight, and therefore, the energy density is large.
In such a laminate type battery, when an electrolytic solution is swollen in a polymer, deformation of the laminate type battery can be suppressed, and therefore, laminate polymer type batteries are also widely put into practical use.
However, the laminate type battery involved such a problem that it is easy to cause blister in a high-temperature atmosphere because its exterior member is soft.
With respect to the problem that blister is easily caused at the time of high-temperature storage, there is proposed a nonaqueous electrolyte secondary battery in which a solid electrolyte interface coating is formed on a negative electrode at the time of initial charge using a nonaqueous electrolytic solution containing a prescribed isocyanate compound (see JP-A-2006-164759 and JP-A-2007-242411).